Buprenorphine is a semi-synthetic opioid and a partial μ-opioid receptor agonist and has the following structure:

Activation of the μ-opioid receptor leads to antinociception and is the pathway by which opioids such as morphine and fentanyl reduce acute and chronic pain. Buprenorphine has advantages over other opioids such as morphine and fentanyl in that it is only a partial instead of a full agonist of the opioid receptor-like receptor 1 (“ORL1”). Activation of ORL1 has been reported to weaken the analgesic effect induced by the activation of the μ-opioid receptor. Additionally, buprenorphine is an antagonist of δ- and κ-opioid receptors, whose activation has anti-analgesic and psychotomimetic effects, respectively. Buprenorphine is also useful in the management of opioid dependence. The slow binding of buprenorphine to the μ-opioid receptor along with its strong affinity allows for pain management at relatively low blood concentrations and the slow disassociation of buprenorphine from the μ-opioid receptor results in a lack of withdrawal symptoms.
Buprenorphine is currently available in transdermal patches, intravenous injection, tablet and film strip formulations. Commercially available buprenorphine formulations include Butrans® (Butrans is a registered trademark of Purdue Pharma L.P.), a 7 day transdermal patch that releases buprenorphine at 5, 10 or 20 mcg/hr, and Temgesic, a 0.2 mg sublingual tablet, are used for the treatment of chronic pain. Buprenexm (Buprenex is a registered trademark of Reckitt Benckiser Healthcare (UK) Limited) is a 0.3 mg/mL injectable solution used for the treatment of acute pain. Subutex® (Subutex is a registered trademark of Reckitt Benckiser Healthcare (UK) Limited) and Suboxone® (Suboxone is a registered trademark of Reckitt Benckiser Healthcare (UK) Limited) are tablets used in the treatment of opioid dependence. Subutex® is available in 2 mg and 8 mg sublingual doses of buprenorphine. Suboxone® contains both buprenorphine and naloxone in a 4:1 ratio. Suboxone® is available in tablet form in 2 mg and 8 mg doses. Suboxone® is also available in a sublingual film strip formulation that dissolves faster and is not lost by accidental swallowing.
Naloxone has the following structure and is synthesized from thebaine:

Naloxone is most commonly used to treat patients suffering from opioid dependence or overdose because it is a competitive μ-opioid antagonist that blocks the effects of opioids.
While there are various formulations currently available, there exists a need in the art for a liquid (i.e., sublingual or intranasal) spray formulation containing buprenorphine or buprenorphine and naloxone, pharmaceutically acceptable salts thereof, or derivatives thereof. Such a formulation should be safe, be easy to administer, have a high bioavailability, and be storage stable.